The official, Kim Chang-son, who serves as Mr. Kim’s de facto chief of staff, arrived in Hanoi on Saturday to discuss logistics with his White House counterpart, Daniel Walsh.

The North Korean leader plans to arrive in Hanoi next Monday to meet with President Nguyen Phu Trong of Vietnam before a second summit meeting with Mr. Trump, slated for Wednesday and Thursday next week, Reuters reported, citing anonymous sources.

While in Vietnam, Mr. Kim plans to visit the Vietnamese manufacturing base of Bac Ninh Province, northeast of Hanoi, and the industrial port city of Haiphong, Reuters said.

Kim Chang-son visited Bac Ninh on Sunday, raising speculation that the North’s leader might go to a smartphone manufacturing plant operated there by South Korea’s Samsung Electronics, the South Korean news agency Yonhap reported. He also went to Ha Long Bay, a popular tourist destination near Haiphong, it said.

Neither South Korean nor Samsung officials would immediately confirm the Reuters and Yonhap reports on Monday.

The brisk activities by the advance team of North Korean officials reflected an eagerness to use Mr. Kim’s second summit meeting with Mr. Trump to elevate his status at home and abroad. No North Korean leader had ever met a sitting American president until Mr. Trump met with Mr. Kim in June in Singapore in an attempt to end the North’s nuclear weapons program.

Mr. Kim’s visit to Vietnam, the first by a North Korean leader since 1964, will also help strengthen relations between the countries’ two ruling Communist parties.

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Mr. Kim, center, and his staff in Hanoi on Saturday.CreditKham/Reuters

North Korea sent air force pilots to help North Vietnam during the Vietnam War. But relations between the two have declined in recent decades, as South Korea has emerged as Vietnam’s biggest foreign investor and Vietnam often served as a way station for North Korean refugees fleeing to South Korea.

Vietnam’s transformation from a rigidly Communist military foe of the United States into one of Asia’s most prosperous economies may prove particularly attractive for Mr. Kim, analysts say. Ever since he began his diplomatic overtures toward the United States and its South Korean allies early last year, Mr. Kim has presented himself as a leader focused on ramping up economic growth.

But despite the frenzied logistical preparations, the United States and North Korea have yet to make substantial progress in ironing out details of a hoped-for denuclearization agreement that they can tout at the end of their meetings, South Korean officials said.

Stephen Biegun, Washington’s top representative in talks with North Korea, was expected to meet with his North Korean counterpart, Kim Hyok-chol, in Hanoi this week to try to cobble together an agreement on what specific actions toward denuclearization the North should take and what “corresponding” steps Washington can offer in reward.

The first summit meeting between Mr. Kim and Mr. Trump was criticized for lacking such details, producing only a vague commitment to “work toward complete denuclearization of the Korean Peninsula.”

During Mr. Biegun’s visit to Pyongyang this month, North Korea reaffirmed its offer to dismantle its Yongbyon nuclear complex, which houses facilities for producing nuclear bomb fuel, and demanded that Washington ease sanctions.

“We are aiming to get as far down the road as we can in what’s now a couple weeks,” Secretary of State Mike Pompeo said last week about Washington’s pre-summit negotiations with the North Koreans. But it remained unclear whether Mr. Biegun had enough time to work out a deal substantial enough to dispel deep skepticism around Mr. Trump’s second encounter with Mr. Kim.

Mr. Trump has repeatedly claimed that his diplomacy with Mr. Kim has defused the crisis over North Korea’s nuclear threats. On Friday, he boasted that Prime Minister Shinzo Abe of Japan, a hawkish politician on North Korea, had nominated him for the Nobel Peace Prize and sent him a “beautiful copy” of the recommendation letter.

Mr. Abe, speaking to Parliament on Monday, declined to confirm or deny that he had made such a nomination.